The invention is directed generally to treatment of effluent from landfilled refuse and, more specifically, for treating the leachate from such refuse.
In recent years, a growing number of communities have turned from the traditional open community dump for refuse disposal to the so-called "sanitary landfill" system. Although most state codes require a four-foot buffer zone between refuse and the high water table, experience has shown that landfills normally produce a highly-potent fluid waste or leachate, but this leachate has a propensity for traveling considerable distances away from its point of origin. This has created a considerable pollution problem which cannot be eliminated by increasing the degree of separation between the refuse and the high water table.
It has been proposed to use impermeable liners to catch and treat leachate and to treat the leachate as conventional systems. Since the leachate is much more toxic than conventional raw sewage, many communities are reluctant to add the leachate to the local waste water treatment plant. This toxicity is due, in part, to the presence of heavy metals. It is also due to the biochemical oxygen demand which is a value obtained from a five day test in a manner well-known in the art and which is expressed as "BOD5 mg/L" (milligrams per liter). The BOD5 of raw sewage is approximately 300 mg/L while that of refuse leachate may be as high as 30,000 mg/L. Since conventional waste water treatment plants are not designed to treat effluent of such high toxicity, normal operation would be upset and water contamination of local streams and ground water would result if one attempted to purify it in such a treatment plant.
Also, the expense of collecting and transporting the refuse leachate from the landfill site to the local waste water treatment plant could prove to be prohibitive.
In addition to the toxicity of heavy metals, it appears that landfill leachates pose a serious bacteriological and viral threat to ground and surface waters. If leachates can be contained within the soil, and are forced to flow through a semi-permeable stratum, considerable screening or absorption can occur, but all too often they have been found to break out at the face of the landfill area and to flow over land to adjacent surface waters. If these surface waters are used for potable water supplies or contact recreation, there may be a need for increased attention to the micro-biological health implication associated with leachates. These and other difficulties experienced with the prior art systems have been obviated by the present invention.
It is, therefore, an outstanding object of the invention to provide an on-site system and method of treating leachate.
Another object of the invention is the provision of a system for treating highly toxic leachates from a landfill and reducing them to a safe, acceptable level for release into the environment.
A further object of the present invention is the provision of a treatment system for leachates which is efficient and capable of large scale continuous treatment of highly toxic leachates.
It is another object of the invention to provide a leachate-treating system which is relatively inexpensive to operate.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of elements and conditions set forth in the specification and covered by the claims appended hereto.